The present invention relates generally to a device for stacking and compressing a plurality of soft elements, especially boards of fibrous insulating material, comprising a stacking shaft (14), in which the elements are capable of being stacked.
As a rule, equipment for wrapping insulating material is connected directly to a production line where the material is sawn and/or cut in specified sizes. This is a continuous process where the boards are usually supplied at a rate of one board per second or faster.
When wrapping pads or boards of a soft material, such as insulating material, a method has since long been applied, in which rectangular boards are stacked into a stack, compressed in the direction of stacking into a package, and then provided with a coating of a thin flexible material, such as plastic, which maintains the package in its compressed state.
According to a frequently used method, the packages are inserted in their longitudinal direction with the aid of some type of pushing means into an opening of a sack or tube of plastic, which is then possibly welded together at its open end.
According to the above method, the sides of the package are subjected, perpendicular to the direction of compression, to a mechanical pressure, which results in an unfavourable pressure gradient. There is a risk that the fibres of the material, if any, will be damaged if excessive mechanical pressure is applied to the package. This is a major problem since most insulating materials consist of fibre materials which are sensitive to pressure being applied transversely of the fibres.
Furthermore, the compressed package, while being fed, frequently passes irregularities in the conveying paths, such as bumps or gaps. These irregularities are propagated through a plurality of boards in the compressed package and result in additional pressure gradients and damage the fibres.
The object of the present invention is to provide automatic stacking and compressing, which in every respect are satisfactory, of an insulating material without the material being subjected to detrimental pressure gradients.
According to the invention, this object is achieved by a device which is of the type stated by way of introduction and which comprises receiving means comprising first drive means which are arranged on two opposite sides of the stacking shaft and to each of which at least two receiving surfaces extending along the width of the shaft are arranged, which in pairs are arranged in level with each other and are movable by said first drive means in the vertical direction of said shaft, and compressing means comprising second drive means which are arranged on two opposite sides of the stacking shaft and which are individually movable in relation to said first drive means, to each of which at least two compressing surfaces extending along the width of the shaft are arranged, so that the receiving surfaces in pairs are arranged in level with each other and are movable by said second drive means in the vertical direction of said shaft, each pair of receiving surfaces being adapted to successively receive elements, one by one, and to support the same to form a stack, and each pair of compressing surfaces being adapted to be individually movable from above in the direction of the stack, for compressing the same.
This construction renders stacking and compressing in a continuous process possible, in which the soft elements are not subjected to considerable power gradients.
The pair of receiving surfaces which supports the stack can be adapted to be gradually movable downwards as the tack grows in the vertical direction. As a result, the entire height of the shaft is utilised.
The first and second drive means may consist of elongate, flexible elements, preferably chains, which run in individually moving paths between deflecting means adjagent to the upper and lower part of the shaft, and which support said receiving surfaces and compressing surfaces, respectively, thereby forming a double paternoster-like arrangement. Preferably said first and second flexible elements run individually along an essentially common path, and said compressing surfaces and receiving surfaces are arranged alternatingly along said path. The receiving means and the compressing means each comprise preferably two pairs of receiving surfaces and two pairs of compressing surfaces.
This construction results in the receiving means being operable individually in relation to the compressing means, so that a stack can be compressed by the compressing means while at the same time a new stack can be received by the receiving means.
The device further comprises at least one first conveying means which is movable between a first deactivated position in which it is located outside the stacking shaft, and a second activated position in which it is located parallel with the compressing surfaces and contacts the upper side of the stack so as to allow, without frictional forces acting against the motion, conveyance of the stack transversely of the compressing direction.
With this discharge from the stacking area, the motion occurs without frictional forces acting on the package, which result in conventional discharge in similar situations, where, while discharging, compressing means are in contact with the material in the package and thus cause friction. Moreover, no pressing force need be applied to the package, which also normally occurs in the form of a hydraulic discharging means or the like. The compressing process according to this embodiment thus affords handling which is very gentle to the material.
Preferably, the movable conveying means consists of one or more belt conveyors which, in cooperation with a belt conveyor located under the stack, can discharge the stack. Although it is convenient for all belt conveyors to be driven, this is not necessary. Thus, for example one or more of the belt conveyors moved towards the package may have no drive and can only afford elimination of frictional forces.
According to a further embodiment of the invention, the step of compressing the stack comprises conveying of the stack between belt conveyors which are located on two opposite sides of the stack and which converge. Compressing the stack in this fashion results in a gradual compression which is gentle to the material, especially to fibrous materials.